IPC Unix消息隊列線程安全嗎？
[英]Are IPC Unix Message Queue Thread Safe?
問題描述
我在下面的代碼中，了解了Linux中消息隊列的線程安全性。 但不確定該程序為什么會卡住。 雖然在應用正確的鎖之后它不會卡住。但是如果消息隊列是線程安全的，那么為什么程序會卡住。或者我在那里錯過了一個技巧？ 小幫助或建議將有助於深入。
#include <cstdio>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <cstdlib>
#include <cstring>
#include <errno.h>
#include <iostream>
#include <string>
#include <thread>
using namespace std;
struct mesg_buffer // MQ Structure
{
long mesg_type;
char mesg_text[100];
};
class MQ_Wrapper // Wrapper class
{
key_t key;
int msgid;
public:
MQ_Wrapper()
{
key = ftok("progfiles_other", 65); // creating key
msgid = msgget(key, 0666 | IPC_CREAT ); // creating message
// queue id
}
~MQ_Wrapper() // removing mqueue in destructor
{
remove_queue();
}
void remove_queue() // removing m queue
{
msgctl(msgid, IPC_RMID, NULL);
}
bool receive_message() // For receiving mesd
{
mesg_buffer message;
if( msgrcv(msgid, &message, sizeof(message), 0, IPC_NOWAIT) != -1 )
{
printf("Data Received is : %s \n",message.mesg_text);
}
else
{
printf("Receving Failed : "); //p
return false;
}
return true;
}
void send_message(int count)
{
mesg_buffer message;
message.mesg_type = count;
char str[25];
sprintf(str,"Hello Friends %ld",message.mesg_type);
strcpy(message.mesg_text,str);
if (msgsnd(msgid, &message, sizeof(message), 0) == 0)
{
printf("Data send is : %s \n", message.mesg_text);
// getting stuck here
}
else
{
printf("Sending Failed\n");
}
}
};
MQ_Wrapper mq; // Global object
// all local variables used
void send_func(bool status)
{
for(int i = 1 ; i < 501 ; i++)
{
if(i%2 == status)
mq.send_message(i);
}
}
void receive_func()
{
while(1) // infinite loop
{
if (mq.receive_message() == false)
break;
}
}
int main()
{
thread send1(send_func,true); // thread 1
thread send2(send_func,false); // thread 2
thread receive1(receive_func); // thread 3
thread receive2(receive_func); // thread 4
send1.join();
send2.join();
receive1.join();
receive2.join();
return 0;
}
以下是短輸出端
FULL OUTPUT:
============
Data send is : Hello Friends 2
Data send is : Hello Friends 4
Data send is : Hello Friends 6
Data send is : Hello Friends 8
Data send is : Hello Friends 10
Data send is : Hello Friends 12
Data send is : Hello Friends 14
Data send is : Hello Friends 16
Data send is : Hello Friends 18
Data send is : Hello Friends 20
Data send is : Hello Friends 22
Data send is : Hello Friends 24
Data send is : Hello Friends 26
Data send is : Hello Friends 28
Data send is : Hello Friends 30
Data send is : Hello Friends 32
Data send is : Hello Friends 34
Data send is : Hello Friends 36
Data send is : Hello Friends 38
Data send is : Hello Friends 40
Data send is : Hello Friends 42
Data send is : Hello Friends 44
Data send is : Hello Friends 46
Data send is : Hello Friends 48
Data send is : Hello Friends 50
Data send is : Hello Friends 52
Data send is : Hello Friends 54
Data send is : Hello Friends 56
Data send is : Hello Friends 58
Data send is : Hello Friends 60
Data send is : Hello Friends 62
Data send is : Hello Friends 64
Data send is : Hello Friends 66
Data send is : Hello Friends 68
Data send is : Hello Friends 166
Data send is : Hello Friends 168
Data send is : Hello Friends 170
Data send is : Hello Friends 172
Data send is : Hello Friends 174
Data send is : Hello Friends 176
Data send is : Hello Friends 178
Data send is : Hello Friends 180
Data send is : Hello Friends 182
Data send is : Hello Friends 184
Data send is : Hello Friends 186
Data send is : Hello Friends 188
Data send is : Hello Friends 190
Data send is : Hello Friends 192
Data send is : Hello Friends 194
Data send is : Hello Friends 196
Data send is : Hello Friends 198
Data send is : Hello Friends 200
Data send is : Hello Friends 202
Data send is : Hello Friends 204
Data send is : Hello Friends 206
Data send is : Hello Friends 208
Data send is : Hello Friends 210
Data send is : Hello Friends 212
Data send is : Hello Friends 214
Data send is : Hello Friends 216
Data send is : Hello Friends 218
Data send is : Hello Friends 220
Data send is : Hello Friends 222
Data send is : Hello Friends 224
Data send is : Hello Friends 226
Data send is : Hello Friends 228
Data send is : Hello Friends 230
Data send is : Hello Friends 232
Data send is : Hello Friends 234
Data send is : Hello Friends 236
Data send is : Hello Friends 238
Data send is : Hello Friends 240
Data send is : Hello Friends 242
Data send is : Hello Friends 244
Data send is : Hello Friends 246
Data send is : Hello Friends 248
Data send is : Hello Friends 250
Data send is : Hello Friends 252
Data send is : Hello Friends 254
Data send is : Hello Friends 256
Data send is : Hello Friends 258
Data send is : Hello Friends 260
Data send is : Hello Friends 262
Data send is : Hello Friends 264
Data send is : Hello Friends 266
Data send is : Hello Friends 268
Data send is : Hello Friends 270
Data send is : Hello Friends 272
Data send is : Hello Friends 274
Data send is : Hello Friends 276
Data send is : Hello Friends 278
Data send is : Hello Friends 280
Data send is : Hello Friends 282
Data send is : Hello Friends 284
Data send is : Hello Friends 286
Data send is : Hello Friends 288
Data send is : Hello Friends 290
Data send is : Hello Friends 292
Data Received is : Hello Friends 2
Data Received is : Hello Friends 4
Data Received is : Hello Friends 6
Data Received is : Hello Friends 8
Data Received is : Hello Friends 10
Data Received is : Hello Friends 12
Data Received is : Hello Friends 14
Data Received is : Hello Friends 16
Data Received is : Hello Friends 18
Data Received is : Hello Friends 20
Data Received is : Hello Friends 22
Data Received is : Hello Friends 24
Data Received is : Hello Friends 26
Data Received is : Hello Friends 28
Data Received is : Hello Friends 30
Data Received is : Hello Friends 32
Data Received is : Hello Friends 34
Data Received is : Hello Friends 36
Data Received is : Hello Friends 38
Data Received is : Hello Friends 40
Data Received is : Hello Friends 42
Data Received is : Hello Friends 44
Data Received is : Hello Friends 46
Data Received is : Hello Friends 48
Data Received is : Hello Friends 50
Data Received is : Hello Friends 52
Data Received is : Hello Friends 54
Data Received is : Hello Friends 56
Data Received is : Hello Friends 58
Data Received is : Hello Friends 60
Data Received is : Hello Friends 62
Data Received is : Hello Friends 64
Data Received is : Hello Friends 66
Data Received is : Hello Friends 68
Data Received is : Hello Friends 70
Data Received is : Hello Friends 72
Data Received is : Hello Friends 74
Data Received is : Hello Friends 76
Data Received is : Hello Friends 78
Data Received is : Hello Friends 80
Data Received is : Hello Friends 82
Data Received is : Hello Friends 84
Data Received is : Hello Friends 86
Data Received is : Hello Friends 88
Data Received is : Hello Friends 90
Data Received is : Hello Friends 92
Data Received is : Hello Friends 94
Data Received is : Hello Friends 96
Data Received is : Hello Friends 98
Data Received is : Hello Friends 100
Data Received is : Hello Friends 102
Data Received is : Hello Friends 104
Data Received is : Hello Friends 106
Data Received is : Hello Friends 108
Data Received is : Hello Friends 110
Data Received is : Hello Friends 112
Data Received is : Hello Friends 114
Data Received is : Hello Friends 116
Data Received is : Hello Friends 118
Data Received is : Hello Friends 120
Data Received is : Hello Friends 122
Data Received is : Hello Friends 124
Data Received is : Hello Friends 126
Data Received is : Hello Friends 128
Data Received is : Hello Friends 130
Data Received is : Hello Friends 132
Data Received is : Hello Friends 134
Data Received is : Hello Friends 136
Data Received is : Hello Friends 138
Data Received is : Hello Friends 140
Data Received is : Hello Friends 142
Data Received is : Hello Friends 144
Data Received is : Hello Friends 146
Data Received is : Hello Friends 148
Data Received is : Hello Friends 150
Data Received is : Hello Friends 152
Data Received is : Hello Friends 154
Data Received is : Hello Friends 156
Data Received is : Hello Friends 158
Data Received is : Hello Friends 160
Data Received is : Hello Friends 162
Data Received is : Hello Friends 164
Data Received is : Hello Friends 166
Data Received is : Hello Friends 168
Data Received is : Hello Friends 170
Data Received is : Hello Friends 172
Data Received is : Hello Friends 174
Data Received is : Hello Friends 176
Data Received is : Hello Friends 178
Data Received is : Hello Friends 180
Data Received is : Hello Friends 182
Data Received is : Hello Friends 184
Data Received is : Hello Friends 186
Data Received is : Hello Friends 188
Data Received is : Hello Friends 190
Data Received is : Hello Friends 192
Data Received is : Hello Friends 194
Data Received is : Hello Friends 196
Data Received is : Hello Friends 198
Data Received is : Hello Friends 200
Data Received is : Hello Friends 202
Data Received is : Hello Friends 204
Data Received is : Hello Friends 206
Data Received is : Hello Friends 208
Data Received is : Hello Friends 210
Data Received is : Hello Friends 212
Data Received is : Hello Friends 214
Data Received is : Hello Friends 216
Data Received is : Hello Friends 218
Data Received is : Hello Friends 220
Data Received is : Hello Friends 222
Data Received is : Hello Friends 224
Data Received is : Hello Friends 226
Data Received is : Hello Friends 228
Data Received is : Hello Friends 230
Data Received is : Hello Friends 232
Data Received is : Hello Friends 234
Data Received is : Hello Friends 236
Data Received is : Hello Friends 238
Data Received is : Hello Friends 240
Data Received is : Hello Friends 242
Data Received is : Hello Friends 244
Data Received is : Hello Friends 246
Data Received is : Hello Friends 248
Data Received is : Hello Friends 250
Data Received is : Hello Friends 252
Data Received is : Hello Friends 254
Data Received is : Hello Friends 256
Data Received is : Hello Friends 258
Data Received is : Hello Friends 260
Data Received is : Hello Friends 262
Data Received is : Hello Friends 264
Data Received is : Hello Friends 266
Data Received is : Hello Friends 268
Data Received is : Hello Friends 270
Data Received is : Hello Friends 272
Data Received is : Hello Friends 274
Data Received is : Hello Friends 276
Data Received is : Hello Friends 278
Data Received is : Hello Friends 280
Data Received is : Hello Friends 282
Data Received is : Hello Friends 284
Data Received is : Hello Friends 286
Data Received is : Hello Friends 288
Data Received is : Hello Friends 290
Data Received is : Hello Friends 292
Data Received is : Hello Friends 294
Data Received is : Hello Friends 1
Receving Failed : Data send is : Hello Friends 294
Data send is : Hello Friends 296
Data send is : Hello Friends 298
Data send is : Hello Friends 300
Data send is : Hello Friends 302
Data send is : Hello Friends 304
Data send is : Hello Friends 306
Data send is : Hello Friends 308
Data send is : Hello Friends 310
Data send is : Hello Friends 312
Data send is : Hello Friends 314
Data send is : Hello Friends 316
Data send is : Hello Friends 318
Data send is : Hello Friends 320
Data send is : Hello Friends 322
Data send is : Hello Friends 324
Data send is : Hello Friends 326
Data send is : Hello Friends 328
Data send is : Hello Friends 330
Data send is : Hello Friends 332
Data send is : Hello Friends 334
Data send is : Hello Friends 336
Data send is : Hello Friends 338
Data send is : Hello Friends 340
Data send is : Hello Friends 342
Data send is : Hello Friends 344
Data send is : Hello Friends 346
Data send is : Hello Friends 348
Data send is : Hello Friends 350
Data send is : Hello Friends 352
Data send is : Hello Friends 354
Data send is : Hello Friends 356
Data send is : Hello Friends 358
Data send is : Hello Friends 360
Data send is : Hello Friends 362
Data send is : Hello Friends 364
Data send is : Hello Friends 366
Data send is : Hello Friends 368
Data send is : Hello Friends 370
Data send is : Hello Friends 372
Data send is : Hello Friends 374
Data send is : Hello Friends 376
Data send is : Hello Friends 378
Data send is : Hello Friends 380
Data send is : Hello Friends 382
Data send is : Hello Friends 384
Data send is : Hello Friends 386
Data send is : Hello Friends 388
Data send is : Hello Friends 390
Data send is : Hello Friends 392
Data send is : Hello Friends 394
Data send is : Hello Friends 396
Data send is : Hello Friends 398
Data send is : Hello Friends 400
Data send is : Hello Friends 402
Data send is : Hello Friends 404
Data send is : Hello Friends 406
Data send is : Hello Friends 408
Data send is : Hello Friends 410
Data send is : Hello Friends 412
Data send is : Hello Friends 414
Data send is : Hello Friends 416
Data send is : Hello Friends 418
Data send is : Hello Friends 420
Data send is : Hello Friends 422
Data send is : Hello Friends 424
Data send is : Hello Friends 426
Data send is : Hello Friends 428
Data send is : Hello Friends 430
Data send is : Hello Friends 432
Data send is : Hello Friends 434
Data send is : Hello Friends 436
Data send is : Hello Friends 438
Data send is : Hello Friends 440
Data send is : Hello Friends 442
Data send is : Hello Friends 444
Data send is : Hello Friends 446
Data send is : Hello Friends 448
Data send is : Hello Friends 450
Data send is : Hello Friends 452
Data send is : Hello Friends 454
Data send is : Hello Friends 456
Data send is : Hello Friends 458
Data send is : Hello Friends 460
Data send is : Hello Friends 462
Data send is : Hello Friends 464
Data send is : Hello Friends 466
Data send is : Hello Friends 468
Data send is : Hello Friends 470
Data send is : Hello Friends 472
Data send is : Hello Friends 474
Data send is : Hello Friends 476
Data send is : Hello Friends 478
Data send is : Hello Friends 480
Data send is : Hello Friends 482
Data send is : Hello Friends 484
Data send is : Hello Friends 486
Data send is : Hello Friends 488
Data send is : Hello Friends 490
Data send is : Hello Friends 492
Data send is : Hello Friends 494
Data send is : Hello Friends 496
Data send is : Hello Friends 498
Data send is : Hello Friends 500
Data send is : Hello Friends 1
Data send is : Hello Friends 3
Data send is : Hello Friends 5
Data send is : Hello Friends 7
Data send is : Hello Friends 9
Data send is : Hello Friends 11
Data send is : Hello Friends 13
Data send is : Hello Friends 15
Data send is : Hello Friends 17
Data send is : Hello Friends 19
Data send is : Hello Friends 21
Data send is : Hello Friends 23
Data send is : Hello Friends 25
Data send is : Hello Friends 27
Data send is : Hello Friends 29
Data send is : Hello Friends 31
Data send is : Hello Friends 33
Data send is : Hello Friends 35
Data send is : Hello Friends 37
Data send is : Hello Friends 39
Data send is : Hello Friends 41
Data send is : Hello Friends 43
Data send is : Hello Friends 45
Data send is : Hello Friends 47
Data send is : Hello Friends 49
Data send is : Hello Friends 51
Data send is : Hello Friends 53
Data send is : Hello Friends 55
Data send is : Hello Friends 57
Data send is : Hello Friends 59
Data send is : Hello Friends 61
Data send is : Hello Friends 63
Data send is : Hello Friends 65
Data send is : Hello Friends 67
Data send is : Hello Friends 69
Data send is : Hello Friends 71
Data send is : Hello Friends 73
Data send is : Hello Friends 75
Data send is : Hello Friends 77
Data send is : Hello Friends 79
Data send is : Hello Friends 81
Data send is : Hello Friends 83
Data send is : Hello Friends 85
Data send is : Hello Friends 87
Data Received is : Hello Friends 296
Data Received is : Hello Friends 298
Data Received is : Hello Friends 300
Data Received is : Hello Friends 302
Data Received is : Hello Friends 304
Data Received is : Hello Friends 306
Data Received is : Hello Friends 308
Data Received is : Hello Friends 310
Data Received is : Hello Friends 312
Data Received is : Hello Friends 314
Data Received is : Hello Friends 316
Data Received is : Hello Friends 318
Data Received is : Hello Friends 320
Data Received is : Hello Friends 322
Data Received is : Hello Friends 324
Data Received is : Hello Friends 326
Data Received is : Hello Friends 328
Data Received is : Hello Friends 330
Data Received is : Hello Friends 332
Data Received is : Hello Friends 334
Data Received is : Hello Friends 336
Data Received is : Hello Friends 338
Data Received is : Hello Friends 340
Data Received is : Hello Friends 342
Data Received is : Hello Friends 344
Data Received is : Hello Friends 346
Data Received is : Hello Friends 348
Data Received is : Hello Friends 350
Data Received is : Hello Friends 352
Data Received is : Hello Friends 354
Data Received is : Hello Friends 356
Data Received is : Hello Friends 358
Data Received is : Hello Friends 360
Data Received is : Hello Friends 362
Data Received is : Hello Friends 364
Data Received is : Hello Friends 366
Data Received is : Hello Friends 368
Data Received is : Hello Friends 370
Data Received is : Hello Friends 372
Data Received is : Hello Friends 374
Data Received is : Hello Friends 376
Data Received is : Hello Friends 378
Data Received is : Hello Friends 380
Data Received is : Hello Friends 382
Data Received is : Hello Friends 384
Data Received is : Hello Friends 386
Data Received is : Hello Friends 388
Data Received is : Hello Friends 390
Data Received is : Hello Friends 392
Data Received is : Hello Friends 394
Data Received is : Hello Friends 396
Data Received is : Hello Friends 398
Data Received is : Hello Friends 400
Data Received is : Hello Friends 402
Data Received is : Hello Friends 404
Data Received is : Hello Friends 406
Data Received is : Hello Friends 408
Data Received is : Hello Friends 410
Data Received is : Hello Friends 412
Data Received is : Hello Friends 414
Data Received is : Hello Friends 416
Data Received is : Hello Friends 418
Data Received is : Hello Friends 420
Data Received is : Hello Friends 422
Data Received is : Hello Friends 424
Data Received is : Hello Friends 426
Data Received is : Hello Friends 428
Data Received is : Hello Friends 430
Data Received is : Hello Friends 432
Data Received is : Hello Friends 434
Data Received is : Hello Friends 436
Data Received is : Hello Friends 438
Data Received is : Hello Friends 440
Data Received is : Hello Friends 442
Data Received is : Hello Friends 444
Data Received is : Hello Friends 446
Data Received is : Hello Friends 448
Data Received is : Hello Friends 450
Data Received is : Hello Friends 452
Data Received is : Hello Friends 454
Data Received is : Hello Friends 456
Data Received is : Hello Friends 458
Data Received is : Hello Friends 460
Data Received is : Hello Friends 462
Data Received is : Hello Friends 464
Data Received is : Hello Friends 466
Data Received is : Hello Friends 468
Data Received is : Hello Friends 470
Data Received is : Hello Friends 472
Data Received is : Hello Friends 474
Data Received is : Hello Friends 476
Data Received is : Hello Friends 478
Data Received is : Hello Friends 480
Data Received is : Hello Friends 482
Data Received is : Hello Friends 484
Data Received is : Hello Friends 486
Data Received is : Hello Friends 488
Data Received is : Hello Friends 490
Data Received is : Hello Friends 492
Data Received is : Hello Friends 494
Data Received is : Hello Friends 496
Data Received is : Hello Friends 498
Data Received is : Hello Friends 500
Data Received is : Hello Friends 3
Data Received is : Hello Friends 5
Data Received is : Hello Friends 7
Data Received is : Hello Friends 9
Data Received is : Hello Friends 11
Data Received is : Hello Friends 13
Data Received is : Hello Friends 15
Data Received is : Hello Friends 17
Data Received is : Hello Friends 19
Data Received is : Hello Friends 21
Data Received is : Hello Friends 23
Data Received is : Hello Friends 25
Data Received is : Hello Friends 27
Data Received is : Hello Friends 29
Data Received is : Hello Friends 31
Data Received is : Hello Friends 33
Data Received is : Hello Friends 35
Data Received is : Hello Friends 37
Data Received is : Hello Friends 39
Data Received is : Hello Friends 41
Data Received is : Hello Friends 43
Data Received is : Hello Friends 45
Data Received is : Hello Friends 47
Data Received is : Hello Friends 49
Data Received is : Hello Friends 51
Data Received is : Hello Friends 53
Data Received is : Hello Friends 55
Data Received is : Hello Friends 57
Data Received is : Hello Friends 59
Data Received is : Hello Friends 61
Data Received is : Hello Friends 63
Data Received is : Hello Friends 65
Data Received is : Hello Friends 67
Data Received is : Hello Friends 69
Data Received is : Hello Friends 71
Data Received is : Hello Friends 73
Data Received is : Hello Friends 75
Data Received is : Hello Friends 77
Data Received is : Hello Friends 79
Data Received is : Hello Friends 81
Data Received is : Hello Friends 83
Data Received is : Hello Friends 85
Data Received is : Hello Friends 87
Data Received is : Hello Friends 89
Receving Failed : Data send is : Hello Friends 89
Data send is : Hello Friends 91
Data send is : Hello Friends 93
Data send is : Hello Friends 95
Data send is : Hello Friends 97
Data send is : Hello Friends 99
Data send is : Hello Friends 101
Data send is : Hello Friends 103
Data send is : Hello Friends 105
Data send is : Hello Friends 107
Data send is : Hello Friends 109
Data send is : Hello Friends 111
Data send is : Hello Friends 113
Data send is : Hello Friends 115
Data send is : Hello Friends 117
Data send is : Hello Friends 119
Data send is : Hello Friends 121
Data send is : Hello Friends 123
Data send is : Hello Friends 125
Data send is : Hello Friends 127
Data send is : Hello Friends 129
Data send is : Hello Friends 131
Data send is : Hello Friends 133
Data send is : Hello Friends 135
Data send is : Hello Friends 137
Data send is : Hello Friends 139
Data send is : Hello Friends 141
Data send is : Hello Friends 143
Data send is : Hello Friends 145
Data send is : Hello Friends 147
Data send is : Hello Friends 149
Data send is : Hello Friends 151
Data send is : Hello Friends 153
Data send is : Hello Friends 155
Data send is : Hello Friends 157
Data send is : Hello Friends 159
Data send is : Hello Friends 161
Data send is : Hello Friends 163
Data send is : Hello Friends 165
Data send is : Hello Friends 167
Data send is : Hello Friends 169
Data send is : Hello Friends 171
Data send is : Hello Friends 173
Data send is : Hello Friends 175
Data send is : Hello Friends 177
Data send is : Hello Friends 179
Data send is : Hello Friends 181
Data send is : Hello Friends 183
Data send is : Hello Friends 185
Data send is : Hello Friends 187
Data send is : Hello Friends 189
Data send is : Hello Friends 191
Data send is : Hello Friends 193
Data send is : Hello Friends 195
Data send is : Hello Friends 197
Data send is : Hello Friends 199
Data send is : Hello Friends 201
Data send is : Hello Friends 203
Data send is : Hello Friends 205
Data send is : Hello Friends 207
Data send is : Hello Friends 209
Data send is : Hello Friends 211
Data send is : Hello Friends 213
Data send is : Hello Friends 215
Data send is : Hello Friends 217
Data send is : Hello Friends 219
Data send is : Hello Friends 221
Data send is : Hello Friends 223
Data send is : Hello Friends 225
Data send is : Hello Friends 227
Data send is : Hello Friends 229
Data send is : Hello Friends 231
Data send is : Hello Friends 233
Data send is : Hello Friends 235
Data send is : Hello Friends 237
Data send is : Hello Friends 239
Data send is : Hello Friends 241
Data send is : Hello Friends 243
Data send is : Hello Friends 245
Data send is : Hello Friends 247
Data send is : Hello Friends 249
Data send is : Hello Friends 251
Data send is : Hello Friends 253
Data send is : Hello Friends 255
Data send is : Hello Friends 257
Data send is : Hello Friends 259
Data send is : Hello Friends 261
Data send is : Hello Friends 263
Data send is : Hello Friends 265
Data send is : Hello Friends 267
Data send is : Hello Friends 269
Data send is : Hello Friends 271
Data send is : Hello Friends 273
Data send is : Hello Friends 275
Data send is : Hello Friends 277
Data send is : Hello Friends 279
Data send is : Hello Friends 281
Data send is : Hello Friends 283
Data send is : Hello Friends 285
Data send is : Hello Friends 287
Data send is : Hello Friends 289
Data send is : Hello Friends 291
Data send is : Hello Friends 293
Data send is : Hello Friends 295
Data send
卡在上面的線不知道為什么？
1 個解決方案
解決方案1
0 2019-04-01 10:52:29
你的問題有 - imho - 與線程無關。 當您調用msgsnd()該消息將寫入全局隊列。 如果沒有可用的讀取器，則隊列的大小限制為定義的大小，以防止系統溢出。
從msgsnd()的手冊頁
如果隊列中的空間不足，則
msgsnd()的默認行為將阻塞，直到空間可用。
從msgrcv()的手冊頁：
msgrcv()系統調用從msqid指定的隊列中刪除一條消息，並將其放在msgp指向的緩沖區中。
在你的情況下， receive_func失敗並退出，並且receive_func沒有人正在從該隊列中讀取，隊列正在運行，並且一旦它已滿， msgsnd()將阻塞，直到隊列再次有空間。
如果你使用IPC_NOWAIT那么你需要測試你得到的錯誤是否是ENOMSG ，並且不要退出線程但是做一個睡眠：
IPC_NOWAIT
如果隊列中沒有所請求類型的消息，則立即返回。 系統調用失敗，並將errno設置為ENOMSG。
在當前代碼中，如果目前沒有消息可用，則退出文件循環：
if (mq.receive_message() == false)
break;
因此，您需要區分，消息讀取，沒有可用消息或者發生了結束線程的錯誤。
提升消息隊列線程安全且過程安全嗎？
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